Detecting Solenoidal Plasma Turbulence via Laser Polarization Rotation

Area of Science:

• Plasma physics
• Fusion energy research
• Turbulence diagnostics

Background:

• Theoretical studies indicate solenoidal turbulence enhances fusion reactivity.
• No standard diagnostic currently exists to measure solenoidal flows or differentiate turbulence types in high-energy-density plasmas.

Purpose of the Study:

• To propose and validate a novel diagnostic method for measuring solenoidal turbulence.
• To characterize the energy and spatial structure of rotational turbulence.
• To distinguish between solenoidal and compressional turbulence in plasmas.

Main Methods:

• Utilizing cross-polarization scattering of a probe laser.
• Coupling laser scattering to plasma vorticity to measure turbulent vorticity.
• Identifying a diffractive scattering signature analogous to Debye-Scherrer rings.

Main Results:

• The proposed method directly diagnoses the energy and spatial structure of rotational turbulence.
• The technique acts as a calorimeter for shear flows by generating a signal proportional to turbulent vorticity.
• A diffractive scattering signature reveals the distribution of turbulent eddy sizes.

Conclusions:

• The cross-polarization scattering technique offers a direct measurement of solenoidal turbulence.
• This method is applicable to National Ignition Facility (NIF) implosion conditions and other high-energy-density scenarios.
• The technique provides a means to distinguish solenoidal from compressional turbulence, advancing fusion energy research.